Testes de modificações da gravitação em curtas distâncias e a interferometria de nêutrons

Abstract

The advent of braneworld theories has renewed the interest in studying extra dimensions, in particular, due to the implication that gravitation is amplified in short distance domains in these scenarios. Motivated by this prediction, many experiments were carried out in order to test such modifications in gravity on ever smaller length scales. Among these experiments, we highlight neutron interferometry, one of the central themes of our work. In neutron interferometry experiments, the effects of the extra dimensions would manifest themselves through the gravitational interaction between the neutron and the material medium the particle passes through inside the interferometer. However, in zero-thick branes models the internal gravitational potential produced by an extended source, which would describe this interaction, cannot be calculated, since it diverges. In view of this limitation, we consider this question in the context of a thick brane scenario. In this model, it is possible to determine a very relevant quantity in this type of problem, the direct scattering length of the neutron, with which we can identify which physical quantity of this model can be constrained by neutron interferometry. As we will see, the length of direct scattering obtained in this new scenario depends on the nuclear model. One way to avoid this dependency is to consider interferometric experiments in which the source that causes the neutron phase shift is an electric field, as in the Aharonov-Casher (AC) effect test. Contrary to what Newtonian theory establishes, that the resting mass of matter generates the gravitational field, in the case of the AC experiment, the energy of the electric field and its pressure would be the origins of the gravitational field. Thus, as the source that generates the deviation in the neutron wave phase is non-baryonic and relativistic, we argue that this experiment can be seen a test of the short-range behavior of post- Newtonian parameters that measure how much gravity is produced by internal energy and pressure, according to the PPN formalism.